Iron oxide is used in a wide range of fields, such as catalysts, magnetic materials, and pigments, and is a material of great industrial importance. Meanwhile, an iron atom is a substance of great importance in a catalytic reaction while also being a magnetic metal, and is known to have strong magnetization.
Some iron oxides also exhibit magnetism. Examples of typical magnetic iron oxides include needle-shaped γ-Fe2O3 used as a magnetic recording medium, such as cassette tapes and floppy disks (registered trademark); Fe3O4 used as toner for copiers; and the like (Non-Patent Literature (NPL) 1).
Since magnetic iron oxides have high biocompatibility, they are attracting attention as a carrier for use in biomedical technology, such as bioscreening, biosensors, anticancer hyperthermia, drug delivery systems, and MRI. As such, magnetic iron oxide is an attractive material that can be widely used in various fields, such as the ceramic industry, chemical industry, electronic industry, biotech industry, and medical field (NPL 2).
In addition, research is actively under way in terms of nanotechnology. Iron oxide with a very interesting shape, such as a nanotube, nanowire, nanorod, and nanoring, has been produced by controlling the form of the iron oxide at the nano level. Making use of such shapes and the iron oxide properties, there has been some research conducted aimed at applications to templates, microreactors, catalysts, magnetic materials, gas sensors, and the like (NPL 3 to 7).
Patent Literature (PTL) 1 discloses a nucleic acid extraction method comprising allowing nucleic acids to adsorb to amino groups formed on the surface of a particle. PTL 2 discloses that multi-layer dendorimers are formed on the surface of fine particles, amino radicals are formed on the surface of the dendorimers, and nucleic acid or protein is extracted or collected using these amino radicals. PTL 2 further discloses that fine particles of bacteria-derived magnetic bodies may be used as the fine particles and that the bacteria-derived magnetic body consists of a single-phase iron oxide with a size of 50 to 70 nm.